Self-healing plasma electrolytic oxidation coatings doped with benzotriazole loaded halloysite nanotubes on AM50 magnesium alloy

• Simple single-step PEO process for production of self-healing coatings on Mg.
• Benzotriazole loaded halloysite nanotubes incorporated in PEO coatings on Mg.
• The nanotubes increased mechanical properties of PEO coatings.
• PH increase at corrosion sites promoted BTA-mediated nucleation of Mg(OH)2.
• Dense Mg(OH)2 film formed on corrosion sites inhibited pitting corrosion.

Halloysite nanotubes (HNT) and benzotriazole (BTA) loaded HNT were added to a silicate-based electrolyte to produce PEO coatings on AM50 alloy. The coatings were characterised by SEM, EDX and XRD methods. Corrosion behaviour in 3.5 wt.% NaCl was studied by EIS and PDP scans. The HNT increased coating scratch resistance greater than BTA-HNT, although the latter enhanced corrosion resistance due to a self-healing effect. This was triggered by a dense Mg(OH)2 film being formed on corrosion sites following partial coating degradation, preventing pitting corrosion. The single-step process for producing self-healing PEO coatings has good potential in corrosion protection of Mg.

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